The present invention generally relates to apparatus for cooling marine engines, and more particularly relates to apparatus for cooling the housing of a water pump assembly that is used on marine propulsion engines.
Those skilled in the art of marine propulsion engines know that many types of such engines utilize the water in which the boat floats as the means for cooling. Also, many of such engines utilize a water pump assembly to force water through the manifolds of the engine for cooling the same. Typically, such water pump assemblies used on such engines have a rubber vaned impeller and a plastic impeller housing. While the use of a plastic impeller housing is advantageous in terms of cost of production, the rotating impeller may contact the inner surface of the housing and cause wear which can significantly reduce the effective useful life of the housing.
Because of the wear that is often experienced because of the contact, it is common and desirable to apply a liner to the inside of the housing, and such a liner is often made of stainless steel which is pressed or clamped in place. The liner provides a wear resistant surface for the housing.
Under normal operating conditions for such an engine, the heat that is generated by friction resulting from the impeller contacting the housing liner is dissipated by the water flowing through the pump. However, improvements in the design and development of marine engines have resulted in higher speeds of operation. With such higher revving engines, or as a result of other conditions such as conditions which create aerated water resulting in impeller cavitation, more heat may be generated than can be effectively transferred by the water that is actually flowing through the pump. If those conditions occur, thermal damage to the housing and impeller can be sustained.
Accordingly, it is a primary object of the present invention to provide an improved water pump assembly which minimizes the potential for thermal damage to a housing and impeller that would otherwise be susceptible to such damage.
Another object of the present invention is to provide such an improved water pump assembly that achieves thermal protection to a housing that is susceptible to thermal damage under certain conditions, and which achieves such protection with a minimum of expense through an efficient and effective design.
Yet another object of the present invention is in the provision of providing such thermal protection by providing a second chamber adjacent the main chamber in which the impeller is located, so that water is circulated through the second chamber for achieving sufficient heat transfer when the heat transfer resulting from water flow through the main chamber is insufficient.
These and other objects will become apparent upon reading the following detailed description of the present invention, while referring to the attached drawings, in which: